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gh-116909: fix data race with versions in typeobject #134651

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gh-116909: fix data race with versions in typeobject #134651

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1230545
gh-116909: fix data race with versions in typeobject
duaneg May 25, 2025
b3a63c8
Continue to skip test_isolated_subinterpreter under TSAN
duaneg May 26, 2025
33adfc3
Correct assertion that should always fail if reached
duaneg May 25, 2025
d9e1c23
Don't allocate a global type version tag unless required
duaneg May 25, 2025
1eb121d
Update Misc/NEWS.d/next/Core_and_Builtins/2025-05-25-23-55-43.gh-issu…
duaneg May 26, 2025
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-05-25-23-55-43.gh-issue-116909.FGbNKx.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix crash upon importing a static type in a subinterpreter.
32 changes: 27 additions & 5 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,6 @@ class object "PyObject *" "&PyBaseObject_Type"
PyUnicode_CheckExact(name) && \
(PyUnicode_GET_LENGTH(name) <= MCACHE_MAX_ATTR_SIZE)

#define NEXT_GLOBAL_VERSION_TAG _PyRuntime.types.next_version_tag
#define NEXT_VERSION_TAG(interp) \
(interp)->types.next_version_tag

Expand Down Expand Up @@ -1258,6 +1257,25 @@ _PyType_GetVersionForCurrentState(PyTypeObject *tp)
#error "_Py_ATTR_CACHE_UNUSED must be bigger than max"
#endif

static int
get_next_global_version(unsigned int *dest)
{
unsigned int v;
while (1) {
v = _Py_atomic_load_uint_relaxed(&_PyRuntime.types.next_version_tag);

/* Stop if passed the maximum or we successfully updated the field */
if (v > _Py_MAX_GLOBAL_TYPE_VERSION_TAG ||
_Py_atomic_compare_exchange_uint(&_PyRuntime.types.next_version_tag,
&v, v + 1)) {
break;
}
}

*dest = v;
return v <= _Py_MAX_GLOBAL_TYPE_VERSION_TAG;
}

static int
assign_version_tag(PyInterpreterState *interp, PyTypeObject *type)
{
Expand Down Expand Up @@ -1288,11 +1306,12 @@ assign_version_tag(PyInterpreterState *interp, PyTypeObject *type)
}
if (type->tp_flags & Py_TPFLAGS_IMMUTABLETYPE) {
/* static types */
if (NEXT_GLOBAL_VERSION_TAG > _Py_MAX_GLOBAL_TYPE_VERSION_TAG) {
unsigned int version;
if (!get_next_global_version(&version)) {
/* We have run out of version numbers */
return 0;
}
set_version_unlocked(type, NEXT_GLOBAL_VERSION_TAG++);
set_version_unlocked(type, version);
assert (type->tp_version_tag <= _Py_MAX_GLOBAL_TYPE_VERSION_TAG);
}
else {
Expand Down Expand Up @@ -8877,9 +8896,12 @@ init_static_type(PyInterpreterState *interp, PyTypeObject *self,
type_add_flags(self, _Py_TPFLAGS_STATIC_BUILTIN);
type_add_flags(self, Py_TPFLAGS_IMMUTABLETYPE);

assert(NEXT_GLOBAL_VERSION_TAG <= _Py_MAX_GLOBAL_TYPE_VERSION_TAG);
if (self->tp_version_tag == 0) {
_PyType_SetVersion(self, NEXT_GLOBAL_VERSION_TAG++);
unsigned int version;
if (!get_next_global_version(&version)) {
assert(0 && "we have run out of version numbers");
}
_PyType_SetVersion(self, version);
}
}
else {
Expand Down
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